title: A model-based 'varimax' sampling strategy for a heterogeneous population.
abstract: OBJECTIVE
  Sampling strategies are planned to enhance the homogeneity of a sample, hence to minimize confounding errors. A sampling strategy was developed to minimize the variation within population groups. Karachi, the largest urban agglomeration in Pakistan, was used as a model population.
  
  
  METHODS
  Blood groups ABO and Rh factor were determined for 3000 unrelated individuals selected through simple random sampling. Among them five population groups, namely Balochi, Muhajir, Pathan, Punjabi and Sindhi, based on paternal ethnicity were identified. An index was designed to measure the proportion of admixture at parental and grandparental levels. Population models based on index score were proposed. For validation, 175 individuals selected through stratified random sampling were genotyped for the three STR loci CSF1PO, TPOX and TH01.
  
  
  RESULTS
  ANOVA showed significant differences across the population groups for blood groups and STR loci distribution. Gene diversity was higher across the sub-population model than in the agglomerated population. At parental level gene diversities are significantly higher across No admixture models than Admixture models. At grandparental level the difference was not significant.
  
  
  CONCLUSIONS
  A sub-population model with no admixture at parental level was justified for sampling the heterogeneous population of Karachi.
authors.affiliation: Department of Genetics, University of Karachi , Karachi 75270 , Pakistan.
authors.forename: Nuzhat A
authors.initials: NA
authors.lastname: Akram
authors.forename: Shakeel R
authors.initials: SR
authors.lastname: Farooqi
mesh_terms: D000017:ABO Blood-Group System / Q000235:genetics*; D005006:Ethnicity / Q000235:genetics*; D005787:Gene Frequency; D014644:Genetic Variation; D005828:Genetics, Population; D005838:Genotype; D006801:Humans; D010154:Pakistan; D012204:Rh-Hr Blood-Group System / Q000235:genetics*; D012494:Sampling Studies
chemical_list: D000017:ABO Blood-Group System; D012204:Rh-Hr Blood-Group System